When deploying wireless communication networks, there is a balance between coverage and capacity. On the one hand, a few large cells can provide great coverage but at a cost of reduced capacity. On the other hand, a scenario with many small cells creates better capacity and throughput, but may not provide the desired coverage. Hence, there is often a combination of larger cells to provide sufficient coverage with smaller cells to provide better capacity.
However, when the cells get too small, wireless terminals moving in the network cause a great number of handovers which causes significant overhead. Moreover, providing coverage indoors using many small cells can be quite costly, with a radio base station for each such small cell.
One solution to this problem is to use remote radio head devices, where several remote radio head devices connected to the same radio base station share the same cell. In this way, a single radio base station can provide coverage in different parts of the building by placing the remote radio head devices appropriately. Moreover, the wireless device can move between the coverage of different remote radio head devices while staying within the same cell, thus avoiding causing handovers.
There is also another solution with a flexible cell system, where cell configurations are dynamically changed, i.e. dynamic cell splitting and combining of multiple radio heads. Such a system can dynamically optimise between capacity and mobility (handover). In such a system, it is also common to have one cell for multiple radio heads.
However, since only one cell is used for multiple remote radio head devices, the granularity of location determination is quite large. This is a problem in locating the wireless device. Moreover, since the remote radio head devices are often deployed indoors satellite based positioning such as GPS (Global Positioning System) is often unavailable.
WO 2005/032202 presents a method for position determination of mobile stations. Additional control signals comprising virtual base station identification data are distributed in the radio system from well defined locations by e.g. transmitters. Since there is a connection between each virtual base station identification data and the location from where it is transmitted, a mobile terminal can use the information for improving its position estimation according to conventional procedures. However, this requires additional hardware dedicated to transmitting the virtual base station identification data which is costly and creates more complexity than desired.